The Philippines has ordered the suspension of 20 more mines for environmental violations, mostly nickel producers, sparking a jump in nickel ore prices.

In addition to 10 mines already shuttered as part of an audit completed last month, the action brings to 30 the number of suspended mines, 18 of them nickel producers that account for 55.5% of the country's total nickel ore output based on last year's production.

OceanaGold (OTCPK:OCANF-9.1%), the top gold miner in the Philippines and one of the companies facing a suspension, says it has not violated any environmental regulations.

Copper prices hit a six-year low for the fifth time in a week in London, -1.9%, amid worries about China’s economy, and are now down nearly 9% YTD; aluminum, lead, nickel and zinc all fell more than 1%.

Long-dated “copper prices adjusted for producer country FX are mostly unchanged, which underscores the macro nature of the recent declines,” according to Goldman Sachs.

The slump is also heavily biting into industrial and precious metals: Copper is now below $4,500 a metric ton for the first time since 2009, nickel lost more than 5% to its lowest level since 2003, zinc is down 4.2%, and gold is 0.7% lower at $1069 an ounce.

Nickel prices are in rebound mode after falling to a near seven-year low last week, buoyed by market speculation that Glencore (OTCPK:GLCNF) could slash output following cuts to its copper and zinc production.

London Metal Exchange nickel stood at $10,460 a tonne on Tuesday, 15% above the $9,100 it fetched on August 12, its lowest price since December 2008.

Glencore, whose shares have been hammered on debt burden worries, declined to comment on the speculation.

The move is good news for Glencore's stock price too, with shares up more than 11% in London and more than doubling since reaching a record low last week.

Glencore's reduced operations in Australia, Kazakhstan and South America will reduce global zinc supply by 500K metric tons/year, not a trivial amount in a 14.5M tons/year global market.

Zinc has, along with nearly all commodities, been under pressure from oversupply, sliding to a five-year low of $1,601.50/ton on Sept. 28.

Further destocking of zinc and a more visible recovery in China’s industrial activities will be needed to propel a more sustained price rally, says Xiao Fu, head of commodity markets strategy at BOCI Global Commodities.

Industrial metals continue their recent climb, with aluminum, zinc and lead trying to play catch-up with copper, which has gained 5% this week as more miners mothball operations at loss-making mines.

Glencore's (OTCPK:GLNCY, OTCPK:GLCNF) Monday announcement that it will cut 400K metric tons of copper production over the next 18 months at two mines in the Democratic Republic of Congo and Zambia comes in the wake of closures or cutbacks at mines controlled by Freeport McMoRan (FCX+4.3%) and others; shortly after Glencore’s decision, the Chinese operator of the Baluba mine in Zambia said it was suspending operations and cutting jobs.

The closures follow a high level of production outages across the copper industry this year because of bad weather and labor disputes, with the combined effect helping to tighten the difference between supply and demand.

Copper prices are on track for their biggest gains since September on speculation that China would use stimulus measures to jump-start its economy and boost demand for the metal.

Rising oil prices and Chinese stimulus speculation “have changed the focus to the upside and the short-covering has done the rest,” says Saxo Bank's Ole Hansen, adding that “energy is such a big and important part of the commodity sector, and the somewhat improved sentiment there also helps other” raw materials; aluminum and nickel also are rising to multi-week highs.

"We’re in this perverse world where bad news is good news,” says BNP Paribas analyst Stephen Briggs, and "a lot of people are thinking China’s going to join the rest of the world and lower interest rates or [offer] some kind of monetary response."

“Despite the large declines in commodity prices, we see risks as still skewed to the downside over the near-term,” says Goldman Sachs.

Of course, much of the price decline has to do with oil, and Goldman doesn't expect a whole lot more damage as prices have gotten low enough for investors to begin buying excess supplies and putting them in storage. While this may put a floor under the price, says Goldman, it also means prices are likely to stay lower for longer.

"The primary reason for the changes to our forecasts is cost deflation," says the team, noting "actual and anticipated U.S. dollar strength, cheaper energy and other input costs and our expectation of an improvement in mining productivity."

The bank cut its expectations for metals and mined raw materials over the next three years by between 10 and 20 percent.

Bearish on copper (NYSEARCA:JJC) even after a 20% decline over the last year, Goldman cuts its forecast for this year to $5,542 per metric ton from $6,400.

Facing a sustained period of oversupply, iron ore is now seen averaging $66 per ton vs. $80 previously. Gold's forecast is trimmed to $1,089 per ounce from $1,200.

Commodity prices as measured by the Total Return Bloomberg Commodities Index reaches new five-year lows, hit by a strengthening dollar, the prospect of a record grain harvest in the U.S. and concerns over weakening economic growth in China.

The index has dropped more than 12% since the end of June amid falling prices for commodities such as crude oil, soybeans and gold.

Even industrial metals, one of this year’s best performers in commodities, have started to come under pressure; nickel has dropped 10% since the end of June, copper prices are at three-month lows, and iron ore trades below $80/ton for the first time since 2009.

Indonesian officials say there are no plans to withdraw the seven-month old ban on exports of unprocessed nickel ore and bauxite.

The country was the world's top exporter of nickel ore and a major bauxite producer until this past January, when the ban was issued in order to force miners to build smelters.

Last month, the government allowed several firms producing partially processed minerals such as copper concentrate to resume exports, although Indonesia's chief economic minister Chairul Tanjung says the same rationale does not apply to unprocessed exports of nickel ore and bauxite.

"Nickel is different because if you are smelting in Indonesia the added value is much higher than copper," says Tanjung. "Because of that it's a separate issue."

Nickel prices reach two-year highs after New Caledonia's government ordered Vale (VALE-0.4%) to suspend activity after a spill at a local site.

Nickel surged 41% in London trading this year after leading global miner Indonesia barred exports of raw ores in January.

With the nickel market already tightening on Indonesia and possible sanctions against Russia, the news adds to the general sense that the market is facing a supply shortage over the coming months, analysts say.

El Niño has a reputation for triggering sharp run-ups for prices in markets as diverse as nickel, coffee and soybeans, and commodities investors, traders and analysts are bracing for impact at a time when global supplies of many raw materials already are stretched.

Global food prices - which at the start of 2014 were expected to be largely flat this year - could easily climb 15% to record highs in as a little as three months after an El Niño occurs, says World Bank economist James Baffes.

But Société Générale analysts say it is miners, not farmers, who have the most to worry about; since 1991, nickel prices rose the most (13.9%) during El Niño years among commodities the bank tracks.

The WSJ shines a light onto "shadow warehouses," a hidden system of facilities that store tens of millions of tons of aluminum, copper, nickel and zinc across the globe for banks, hedge funds and commodity merchants.

The warehouses operate outside the London Metal Exchange's system, are unregulated, and don't provide details of their holdings. As a result, it's unclear how much metal is held in the shadow system. This lack of visibility could cause major price swings.